If the END is followed by a <statement-label> (before the semicolon), it closes that block and any unclosed interior blocks. If the END is not followed be a <statement-label>, it simply closes the preceding unclosed block.
If a statement-label follows END, the END statement closes the unclosed group or block headed by the nearest preceding DO, SELECT, BEGIN, or PROCEDURE statement having that statement-label. It also closes any unclosed groups or blocks physically within that group or block; this is known as multiple closure.

If a statement-label does not follow END, the END statement closes the one group or block headed by the nearest preceding DO, SELECT, BEGIN, or PROCEDURE statement for which there is no other corresponding END statement.
[link|http://publibfp.boulder.ibm.com/cgi-bin/bookmgr/BOOKS/ibm3l101/7.17?DT=19950506201638|IBM Link].